1. Field of Invention
The present invention relates generally to an interconnection board and a connection pin for connecting a user line of a communication system to a communication network, and to a main distribution frame (MDF) having the above interconnection board and connection pin. In particular, the present invention rotates to a multilayer interconnection board and a connection pin, which allow electrically conductive patterns (referred to simply as conductive patterns in this specification) provided on the insulation layers to be electrically connected along desired routes.
Further, the present invention relates to an MDF, which connects user lines to a service node such as an exchange unit in a public communication system by means of the multilayer interconnection board and the connection pin, and to an end exchange station in which the MDF is provided.
2. Description of Related Art
Conventionally, user lines in a telephone communication system are connected to a multilayer interconnection board, and then to a service node such as an exchange unit by a connection pin. Conductive patterns are provided on each insulation layer of the multilayer interconnection board. One conductive pattern on ore insulation layer is connected to another conductive pattern provided on another insulation layer by a connection pin.
FIG. 1 shows a connection pin 76 of the prior art. The connection pin 76 has a non-conductive stem 20 and annular connection patterns 21 provided on the non-conductive stem 20.
FIG. 2 shows a multilayer interconnection board 23 and the connection pins 76J and 76K (generally referred to as 76) therein of the conventional art. A connection pin 76 connects two of the conductive patterns 12A through 12H (generally referred to as 12) of the multilayer interconnection board 23, when inserted into a through-hole 24 extending through the multilayer interconnection board 23.
In FIG. 2, the multilayer interconnection board 23 includes insulation layers 14A through 14H (generally referred to as 14), which are substantially non-conductive, and conductive patterns 12A through 12H (generally referred to as 12) provided on the insulation layers 14A through 14H, respectively. A conductive pattern 12 on one insulation layer 14 is electrically insulated from that on other insulation layers. The conductive patterns 12 are exposed at the inner walls of the through-holes 24.
When a connection pin 76 is inserted into a through-hole 24J or 24K (generally referred to as 24) provided in the multilayer interconnection board 23, the conductive patterns 12 on different insulation layers are electrically connected to each other by the connection patterns 21 of the connection pin 16. As stems 20J and 20K are non-conductive and connection patterns 21L through 210 are conductive, electrical connections are made on each of routes 12A-21L-12B, 12C-21M-12D, 12E-21N-12F and 12G-210-12H.
FIG. 3 shows the electrical routes 12A-21L-12B and 12C-21M-12D shown in FIG. 2, in detail. The conductive patterns 12A and 12B are connected by the connection pattern 21L and the conductive patterns 12C and 12D are connected by the connection pattern 21M. The connection patterns 21L and 21M are electrically insulated from each other.
A conventional connection pin 76 makes only one electrical path between conductive patterns 12 on two different insulation layers. For example, in FIGS. 2 and 3, only one electrical path is made between the conductive patterns 12A and 12B and one other electrical path is made between the conductive patterns 12C and 12D. The conductive patterns 12B and 12C are electrically insulated from each other.
To obtain enough electrical paths in a small volume by the above-mentioned structure, the multilayer interconnection board needs to include eight to ten layers, the production and operation of which require very high precision.